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Fusion bombs obviously fuse hydrogen atoms, using the pressure from a fission bomb. But how much hydrogen does it contain, and how is it stored? AFAIK hydrogen easily drops its electron and escapes as a proton through metal containers. This is a problem for storing hydrogen rocket fuel for long. The free protons also cause damage to whatever structure it passes through. Or does a fusion bomb maybe not need hydrogen gas, like rocket fuel does, but instead some chemical with hydrogen in it, like water?

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  • $\begingroup$ Obligatory: "I could tell you but then I'd have to kill you." An H-bomb requires deuterium, BTW. YOu might enjoy reading "Dark SUn" by Richard Rhodes. $\endgroup$ – Carl Witthoft Jul 31 '15 at 11:39
  • $\begingroup$ As a bonus that I don't think has been mentioned: Tritium gas a a seriously short half life of 12.3 years and produces Helium which not only decreases the yield but "poisons" the neutron multiplication. External storage was mentioned - as soon as reasonably possible before "use" the Tritium is filtered through a Palladium filter to remove the Helium. Too much Helium (amongst many other things) can lead to a "fizzle" where there is less or even no fusion yield with output being more or all fission. Tom Clancy managed a fizzle in "Sum of all fears" and depending on who you believe, .... $\endgroup$ – Russell McMahon Jul 31 '15 at 13:29
  • $\begingroup$ .... so did the Indians in their one H bomb in their 2nd round of nuclear "demonstration" tests. (The centre director said it was a fizzle but this was denied by the program architects and designer - one of whom, "Missile man" and ex Indian President Dr Abdul Kalam, died a few days ago - academic - H bomb man - missile developer - (largely beloved) President - academic. More than most in a lifetime. $\endgroup$ – Russell McMahon Jul 31 '15 at 13:31
  • $\begingroup$ @RussellMcMahon This all sounds like very trivial engineering. Explains why everyone got the H-bomb already half a century ago. [/irony off] $\endgroup$ – LocalFluff Jul 31 '15 at 14:39
  • $\begingroup$ "hydrogen easily drops its electron and escapes as a proton through metal containers. This is a problem for storing hydrogen rocket fuel for long. The free protons also cause damage to whatever structure it passes through." That's a terrible explanation of hydrogen leakage and corrosion. $\endgroup$ – Mithoron Jul 31 '15 at 16:51
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Look up Lithium deuteride: a form of lithium hydride where the hydrogen is all deuterium: this will give you most of your answers.

The main fusion[1] reaction that lets slip most of the energy and thus the horrendous blast in a fusion bomb is:

$$_1^2 D + _1^3 T \rightarrow _2^4 He (3.5{\rm MeV}) + _0^1 n (14.1{\rm MeV})\tag{1}$$

Here I've written $D$ for deuterium and $T$ for tritium.

The fusion fuel is $Li\,D$, where the lithium comprises both the commonest Lithium-7 ($_3^7 Li$) isotope together with Lithium-6 ($_3^6 Li$).

During the explosion, the fusion fuel is crushed by the energy of a fission primary nuclear blast. The fusion fuel has a fissionable center (a "spark plug"); as this is crushed it too begins fissioning and lets slip neutrons from the fission chain reaction. The neutrons react with the lithium part of the fuel:

$$_3^6 Li + _0^1 n\rightarrow _2^4 He (2.05{\rm MeV}) + _1^3 T(2.75{\rm MeV})\tag{2}$$

and the tritium that is swiftly produced then undergoes the main reaction in (1). Reaction (1) also produces neutrons to breed new tritium.

The $_3^6 Li$ is the one that undergoes the reaction most readily. However, Lithium-7 also produces tritium:

$$_3^7 Li + _0^1 n\rightarrow _2^4 He + _1^3 T + _0^1 n\tag{3}$$

albeit not quite as readily. One of the worst all time "industrial" accidents was the US Castle Bravo nuclear test in 1954 of the first bomb using the dry lithium deuteride fuel (before that, cryogenic deuterium was used in test bombs). Here, the yield of the bomb was calculated assuming that only the $_3^6 Li$ would be converted to tritium fuel. Natural lithium with the $_3^6 Li$ enriched was made for the test, and the remaining $_3^7 Li$ was assumed to be inert. However, the unforeseen reaction (3) meant that the actual energy let slip by the bomb was about two and a half times as great as that calculated. The bunker housing investigators controlling the test only barely withstood the blast, and the huge amounts of unforeseen nuclear fallout was scattered over inhabited atolls which had to be evacuated in the Marshall and many people there never went back to their homes. Tragically a Japanese fishing boat was also caught up in the fallout and the crew, unlike the test investigators, were unaware of the hazard from the ash that fell on their boat and took no safety precautions.

[1]. Many thermonuclear bombs get much of their destructive power from fission: the fusion outputs high energy neutrons which then drench fissile material. The latter efficiently and swiftly undegoes fission: since it is being drenched with enough neutrons to fission a sizeable fraction of the fission fuel, it is not relying on a swift buildup of a chain reaction to fission fuel before the bomb is torn apart, thus quenching the reaction.

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  • $\begingroup$ To add to your foot note, if memory serves (which it easily might not), the DT reaction is ~18MeV (as noted), while a uranium fission releases ~180MeV. $\endgroup$ – Jon Custer Jul 31 '15 at 12:31
  • $\begingroup$ Unlucky Dragon :-(. Not to mention that they were accused of being in a prohibited area in an attempt to hide culpability :-(. | I like "Industrial "accident" - never seen it that way before. $\endgroup$ – Russell McMahon Jul 31 '15 at 12:45
  • $\begingroup$ @RussellMcMahon I wasn't going to mention the name of the boat: it sounds too much like one is poking fun. $\endgroup$ – WetSavannaAnimal Jul 31 '15 at 12:53
  • $\begingroup$ @WetSavannaAnimalakaRodVance Fair enough - certainly no fun poking intended on my part. I'm probably more accustomed to Asian naming customs than some so would not see it as unusual.(I've spent about 6 months in China on multiple visits since 2007). I've long thought the name ironic. | FWIW the 'Rainbow Warrior' (another memorable name) was sunk about 5 miles from where I'm sitting now - on its way to another nuclear bombing. Only one person died that time. $\endgroup$ – Russell McMahon Jul 31 '15 at 13:15
  • $\begingroup$ @RussellMcMahon No I didn't think you were. It's simply I don't like naming the boat. $\endgroup$ – WetSavannaAnimal Jul 31 '15 at 13:28
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Generally, you are correct, and trying to store gaseous hydrogen for long periods of time without significant losses doesn't work. The usual way around this is use lithium deuteride, a solid compound, as the main fuel in the fusion portion of the device (the secondary).

Deuterium/tritium is also used in the fission primary. According to http://nuclearweaponarchive.org/Nwfaq/Nfaq4-3.html the gas is kept (for US weapons) in an exterior tank and introduced into the core just prior to detonation. The amount of D/T is relatively small, so apparently a thick-walled reservoir is adequate. It also makes regular replenishment possible without completely disassembling the device.

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